The Evolution of Communicating the Uncertainty of Climate Change to Policymakers: A Study of IPCC Synthesis Reports - MDPI
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Communication
The Evolution of Communicating the Uncertainty of Climate
Change to Policymakers: A Study of IPCC Synthesis Reports
Tomas Molina 1,* and Ernest Abadal 2
1 Applied Physics Department, University of Barcelona, 08028 Barcelona, Spain
2 Faculty of Information and Audiovisual Media, University of Barcelona, 08014 Barcelona, Spain;
abadal@ub.edu
* Correspondence: tomasmolinabosch@ub.edu
Abstract: The Intergovernmental Panel on Climate Change (IPCC) reports on climate change have
served to alert both the public and policymakers about the scope of the predicted changes and the
effects they would have on natural and economic systems. The first IPCC report was published in
1990, since which time a further four have been produced. The aim of this study was to conduct a
content analysis of the IPCC Summaries for Policymakers in order to determine the degree of cer-
tainty associated with the statements they contain. For each of the reports we analyzed all state-
ments containing expressions indicating the corresponding level of confidence. The aggregated re-
sults show a shift over time towards higher certainty levels, implying a “Call to action” (from 32.8%
of statements in IPCC2 to 70.2% in IPCC5). With regard to the international agreements drawn up
to tackle climate change, the growing level of confidence expressed in the IPCC Summaries for Pol-
icymakers reports might have been a relevant factor in the history of decision making.
Keywords: uncertainty; climate change; decision making; content study; IPCC
Citation: Molina, T.; Abadal, E. The
Evolution of Communicating the
Uncertainty of Climate Change to
Policymakers: A Study of IPCC
1. Introduction
Synthesis Reports. Sustainability
2021, 13, 2466. https://doi.org/ One of the main sources of information about climate change—that is, about the cur-
10.3390/su13052466 rent weather and climate data assessments and the science involved, the vulnerabilities
associated with that change and the different strategies of adaptation and mitigation, and
Academic Editor: João Santos with a global world perspective—is the Intergovernmental Panel on Climate Change
(IPCC), an international body of the United Nations that was established in 1988 by the
Received: 3 February 2021 World Meteorological Organization (WMO) and the United Nations Environment Pro-
Accepted: 20 February 2021 gram (UNEP). [1,2] The most widely read section of the IPCC reports is the Summary for
Published: 25 February 2021
Policymakers [3] and these have served to alert both the public and policymakers about
the scope of predicted climate changes and the effects they would have on natural and
Publisher’s Note: MDPI stays neu-
economic systems.
tral with regard to jurisdictional
claims in published maps and institu-
The first IPCC report was published in 1990, since which time a further four have
tional affiliations.
been produced. In the first stage of report preparation, a team of internationally recog-
nized experts with extensive peer-reviewed research experience in their field, produce a
detailed draft document setting out the current state of scientific knowledge according to
the peer-reviewed literature. Once this draft report has been externally reviewed, an Ex-
Copyright: © 2021 by the authors. ecutive Summary aimed at policymakers, and based closely on the scientific text, is drawn
Licensee MDPI, Basel, Switzerland. up with input from government representatives.
This article is an open access article The IPCC reports gather the results of three working groups: Working Group I (WGI)
distributed under the terms and examines the physical science underpinning climate change and its possible future evo-
conditions of the Creative Commons lution; Working Group II (WGII) assesses the impacts of climate change and the vulnera-
Attribution (CC BY) license bilities of natural and economic systems to it, including options for adaptation; and Work-
(http://creativecommons.org/licenses ing Group III (WGIII) focuses on climate change mitigation, exploring methods for limit-
/by/4.0/). ing or preventing greenhouse gas emissions [4]. The climate projections made over the
Sustainability 2021, 13, 2466. https://doi.org/10.3390/su13052466 www.mdpi.com/journal/sustainabilitySustainability 2021, 13, 2466 2 of 12
thirty years since the first IPCC report was published have been highly accurate with re-
gard to the predicted increases in CO2 levels and temperature, although they have proved
to be underestimates in terms of observed sea level rises [5–7].
Scientific knowledge has evolved considerably over this thirty-year period, as have
the ways in which it is communicated, both to professional audiences and to the public at
large. Communicating science to the general public is always challenging [8] (Seacrest et
al. 2007), but in the case of climate science there are a number of particular difficulties
related to how the level of scientific evidence is expressed, the degree of agreement among
experts and researchers on each topic, the level of confidence in scientific methods and
data, and the likelihood associated with the results of the mathematical models used to
predict future changes [9].
During these three decades of IPCC climate reports, the level of certainty about the
scientific assessments given to the public has increased, though there is not much litera-
ture on this evolution.
At any time during these years, once the current and latest scientific information
available from the scientific community has been released in peer-reviewed scientific pa-
pers and the most relevant incorporated into every IPCC report, those scientific assess-
ments are used by policymakers to draw up treaties and protocols for tackling climate
change. How ambitious these protocols have been would depend, at some point, on poli-
cymakers’ perceptions regarding the degree of urgency and the need to take specific ac-
tion. It is worth noting here that, according to one recent study, the tone of the probabil-
istic language used by the IPCC tends to be conservative, with the majority of climate
findings being assigned an intermediate level of confidence [10] which may in turn favor
conservatism and inaction among policymakers.
By examining how the level of confidence, agreement, evidence and likelihood in the
climate science described in the IPCC Summaries for Policymakers has evolved over the
past thirty years, we can track the level of uncertainty in the information communicated
to policymakers. As already noted, communicating climate science poses a particular set
of challenges, not least the fact that the audience for the IPCC reports comprises govern-
ment agencies, the media and, to a lesser extent, the general public, each of whom may
interpret the results in light of their own special interests, focusing on elements which
differ from those which scientists wished to highlight [11,12]. Consequently, both the
structure of the reports and the kind of language used will also be key factors in getting
the message across.
Some authors have studied the readability of IPCC reports and have compared those
produced by different working groups with the Summaries for Policymakers [3] im-
portantly, they found that not only has readability not improved significantly over time,
but it has also actually decreased between the two most recent reports (IPCC4 and IPCC5).
Other studies have examined, across several different countries and languages, the
public’s interpretation of the probabilistic statements used in IPCC reports [13]. Although
the language in which the report was read was a factor, the authors found that laypeople
tend to interpret the level of certainty of statements as being around 50%, much less ex-
treme than the reports’ authors intended.
Decision making depends on the level of certainty on the premises and information
given to the subjects. [14].Difficult decisions need well informed subjects, especially when
uncertainty is involved in the knowledge related to decision making. This problem is well
known in the fields of medical decision making and ethics [15,16]. The level of certainty,
and the manners in which it is communicated to the decision makers, plays an important
role in whether the subjects decide to take action. [17]
In IPCC5 and based on the guidance note for authors [18], the certainty of scientific
statements is ranked using qualifiers of evidence (from limited to robust), agreement
(from low to high), confidence (from very low to very high) and likelihood (from excep-
tionally unlikely to virtually certain). Although some authors have raised doubts about
the treatment of uncertainties in the Fifth Assessment Report(AR5) [19]the report doesSustainability 2021, 13, 2466 3 of 12
enable a detailed analysis of the level of confidence associated with the statements it con-
tains, since the corresponding expressions appear in italics and in brackets. [10] analyzed
the report of WG1 in IPCC5 and counted the frequency of qualifiers for all statements
made, assigning a numerical value so as to calculate a mean score for the report as a whole.
They concluded that the way in which probabilistic language was used by the IPCC fa-
vored inaction among policymakers.
The aim of the present study is to analyze the content of IPCC Summaries for Policy-
makers in order to determine the degree of certainty associated with the statements they
contain. We also examine changes over time in the level of confidence expressed in each
of the reports that have been made available to policymakers and society in general.
2. Materials and Methods
The source material for this study is the Executive Summaries that have been ap-
proved by governments and which contain a Summary for Policymakers of the key con-
clusions reached by each of the working groups. The specific sources consulted for our
analysis were as follows:
1. Executive Summary First Assessment Report (FAR)[20]
In addition to the Executive Summary itself, the FAR also includes a Summary for
Policymakers setting out the conclusions reached by the three working groups.
2. Summary for Policymakers WG I/II/III Second Assessment Report, (SAR) [21]
This Summary for Policymakers contains a chapter by each working group.
3. Synthesis Report—Summary for Policymakers Third Assessment Report (TAR/AR3)
[22]
This Synthesis Report includes a Summary for Policymakers written in a question-
and-answer format, with no clear differentiation between the findings and conclusions of
the different working groups.
4. Synthesis Report —Summary for Policymakers Forth Assessment Report, AR4 [23]
5. Synthesis Report—Summary for Policymakers Fifth Assessment Report, AR5 [24]
In addition to a Synthesis Report, AR4 and AR5 include a Summary for Policymakers
that describes the findings and conclusions of the three working groups.
The first IPCC report was published in 1990 (prior to the internet age and hence in
paper format), with a supplement appearing in 1992. It is descriptive in tone and designed
to be informative for a nonspecialist audience, with very few references to the level of
certainty of the data and projections, although the presumption is that it represents the
scientific consensus of the day [25]. This latter aspect generated considerable political and
scientific rise to numerous counter statements and denials with regard to the report’s con-
tent [26]. We do not consider this report in our analysis of changes over time in the level
of uncertainty, although we do discuss its communicative aspects.
Our analysis is based on the official and original English version: for each report we
perform a content analysis of all sentences containing expressions related to the certainty
of the scientific statement being made, without taking into account the text of figure leg-
ends or tables. The content analysis uses the categories (qualifiers) described in AR5,
which is the report that most specifically describes the treatment of uncertainties. Thus,
this report served as the basis for establishing the levels of uncertainty of statements made
in previous reports, where the definition was less developed, and which are summarized
in Table 1 (the complete version can be found in Annex 1). The table shows some of the
equivalences between the different reports for each level of uncertainty.Sustainability 2021, 13, 2466 4 of 12
Table 1. List of expressions referring to the level of uncertainty of the statements made in the reports studied.
IPCC5 (AR5) IPCC3 (TAR/AR3)
Ranked IPCC4 (AR4) (2007) IPCC2 (SAR) (1995)
(2014) (2001)
Clearly will..., are broadly
Robust Evidence,
Unequivocal, High Virtually certain, very consistent..., already are
High agreement,
agreement, Very high likely, Human activi- widely used..., systems
Very high confi-
confidence, very ties have… new and can easily accommodate,
Very High dence, virtually
likely, Observational stronger evidence... literature provide strong
(5) certain 99–100%,
Evidence, very un- are projected to in- support for..., is a high pri-
very likely 90–
likely (in positive crease… ority..., is widely recog-
100%, Extremely
way) etc. nized to be....
likely 95-100%
etc...
Likely, most likely will,
high confidence,
High confidence, more likely that actual
likely, high to medium
likely, more likely outcomes..., Most of the
confidence, ...are con-
High confidence, than not, show signif- studies..., most convincing
sistent with..., ... is
likely 66–100%, icant change..., ... recent evidence..., is ex-
High (4) projected to..., ... are
more likely than more than 89%, are pected to ..., will lead to...,
projected to..., ... are at
not 50–100% consistent..., much can expect..., cannot be re-
particular risk of..., ...
evidence, versed..., represents an im-
have been identified...,
etc. portant...,
etc.
etc.
Would probably, several
models indicate..., The
Medium confidence,
Medium evidence, magnitude is uncertain,
medium to high confi-
Medium evidence, medium confidence, but could be..., difficult to
dence, small uncer-
medium agree- notable lack of... bal- predict, potentially seri-
tainty..., an increasing
Medium ment, medium ance in data and liter- ous..., ... will have to de-
body of..., within pre-
(3) confidence, about ature, ... but uncer- cide to what degree they
sent uncertainties...,
as likely as not 33– tainties... are larger..., want to take... measures...,
there are preliminary
66% ... cannot be ex- cannot position ..., are dif-
indications...,
cluded, etc. ficult to quantify... (R
etc.
low),
etc.
Low confidence, me- There is more confi-
dium to low confi- dence..., considerable pro-
Limited evidence...,
dence, ... is not well gress has been..., climate
there is not clear..., It
Low confidence, quantified, ... rather models have increased our
is difficult to ascer-
Low (2) more unlikely than attributed solely confidence in..., ...changes
tain..., estimates... are
than likely 0–50% to..., ... quantifying the would include considera-
limited, ... remains
relative impact... is dif- ble natural variability,
uncertain
ficult, ... poorly there are still many uncer-
known, etc. tainties, …etc.
Limited evidence, Limited available evi-
Does not achieve a
low agreement, dence., ...ability to quan-
fully integrated assess-
very low confi- Marked scarcity..., tify... is limited...signal
Very Low ment, because on the
dence, extremely understanding of...is still emerging from
(1) incomplete state of
unlikely 0–5%, very limited noise..., ... important un-
knowledge ... no
exceptionally un- certainties remain..., could
demonstrated
likely 0–1%, very differ substantially from...,Sustainability 2021, 13, 2466 5 of 12
unlikely 0–10%, changes..., insufficient ... where confidence re-
unlikely 0–33% data to assess... mains low., ...
etc.
In AR4, the criteria for uncertainty qualifiers are largely the same as in AR5 and they
are also shown in italics, but also appear in other certainty qualifiers that are less stand-
ardized than in AR5. Thus, it is necessary to read the text in order to identify references to
the level of evidence, agreement, certainty and likelihood, and match them to one of the
four levels of uncertainty. This is a limitation of the content analysis which we have sought
to minimize by applying the criteria shown in Table 1, thus enabling comparison of these
statements of confidence.
In the case of AR3 and SAR, uncertainty is expressed in similar but not identical
terms. It is therefore necessary again to study the text of both reports in order to identify
the degree of uncertainty associated with different statements, and thus be in a position
to compare the results of all four reports in terms of how different levels of uncertainty
are expressed.
In order to perform a numerical analysis of results, we counted the number of state-
ments corresponding to each level of certainty in each of the reports studied. Each of the
five categories of uncertainty was assigned a numerical value from 1 to 5, where 1 is Very
Low, 2 Low, 3 Medium, 4 High and 5 Very High[10]. This enabled us to create a rank order
for the different levels of uncertainty.
In a second stage we introduced a further analytic variable, “Call to action”, which
refers to the level of action implied by the most confident statements, compared with that
for statements expressed with a low or medium level of confidence[19]. Thus, we defined
“Call to action” as the sum of statements made with “Very High + High” levels of cer-
tainty, whereas “No call to action” was defined as the sum of statements made with “Me-
dium + Low + Very Low” levels of uncertainty. Studying changes over time in the level of
uncertainty expressed in the Summaries for Policymakers may help to shed light on the
varying levels of action and inaction shown by governments in the context of international
protocols. [27].
3. Results
3.1. Evolution of the Structure and Communicative Aspects of IPCC Reports
The structure and format of the content included in the Summary for Policymakers
of the five reports has changed considerably over time. There are also notable differences
in the length of the summaries; the shortest is 20 pages for AR4 and the longest 38 pages
for SAR, including a separate Summary for each of the three working groups. Table 2these
differences
Table 2. Structure and format of the reports studied.
Year Title of IPCC Report Structure and Format Length
First Assessment Report (FAR) Narrative structure
1990 Executive Summary, Policymaker Summary Informative for a nonspecialist audience. Many figures 24 p.
and tables, and resumes
Second Assessment Report (SAR)
Narrative structure
1995 Summary for Policymakers, by each Working Group 38 p.
Mostly text, with some figures
Structured as questions and answers
Third Assessment Report (TAR/AR3)
Graphs and tables
2001 Summary for Policymakers, Synthesis Report 34 p.
Level of confidence shown in parentheses and sometimes
likelihood too
Fourth Assessment Report (AR4) Fragments highlighted in bold.
2007 Summary for Policymakers, Synthesis Report Graphs and tables 20 p.
Level of likelihood and confidence in italicsSustainability 2021, 13, 2466 6 of 12
Key fragments in boxes
Fifth Assessment Report (AR5) Graphs and tables
2014 Summary for Policymakers, Synthesis Report All levels of uncertainty shown in italics and confidence 32 p.
also in parentheses
The communication of the state of scientific knowledge on climate change began with
the first IPCC report (1990/92), and it was this document that began to define most of the
concepts that would become familiar over the following thirty years. [28,29]. Interestingly,
the notion of scientific “consensus” is not a defining feature of this report[25].; in fact, the
only reference to it is when the lead author of the WG1 summary states that it was not
fully achieved among participating authors. In terms of its style, the report is written in
direct and plain language and it includes many definitions and explanations of phenom-
ena, alongside projections for the future. Although the document proved to be controver-
sial, both scientifically and politically, it was also groundbreaking and made an impact
worldwide [25]. Perhaps its most original contribution was to begin the process of gath-
ering the findings of peer-reviewed research into summary reports that were then ap-
proved by representatives of governments from around the world, hence the name of the
body responsible for the report: Intergovernmental Panel on Climate Change [30].
The second report (1995) is the most extensive as it includes a separate summary by
each of the three working groups. Those by WGI and WGIII consist of extensive text bro-
ken down into chapters, while that by WGII includes tables and figures among the text,
although all three summaries are aimed primarily at nonspecialist audiences. The report
contains numerous conditional statements and also contemplates the possibility of “sur-
prises”, due to the fact that climate changes are, by their nature, “difficult to predict”. The
process of consensus among the various authors who drew up and subsequently revised
the texts begins to more clearly defined in this report [31].
The third report (2001) is structured in the form of nine questions that were formu-
lated in consultation with the Conference of the Parties (COP) to the United Nations
Framework Convention on Climate Change (UNFCCC). These questions were based on
submissions by governments and were approved by the IPCC. The text of the report uses
different colors and bold format, although the latter serves to separate parts of the text
rather than to highlight key points. The report includes statements of both confidence (in
parentheses) and likelihood, although it also contains numerous expressions that qualify
the available knowledge on the various topics addressed.
The fourth report (2007) contains various sections, each with a clear heading, and
uses bold text to summarize some of the statements made previously in the text. These
statements are direct and assertive. We did not consider these statements in our analysis,
unless they included specific reference to the level of confidence, which, in this document,
is indicated in italics.
The fifth report (2014) contains highlighted conclusions that appear in boxes and act
as a lead-in to each section. Once again, we only considered these statements if specific
reference was made to the level of uncertainty. The overall text of this report is highly
structured, and statements and predictions are accompanied by the corresponding level
of confidence and likelihood (always in italics).
Over time the IPCC reports have adopted a more direct tone and more graphics and
visuals [32] when summarizing the key conclusions of the working groups, and the as-
sessment of uncertainty has been incorporated without making the texts more complex,
thanks to the use of clearly defined and easily identifiable terms (in italics) to indicate the
level of confidence and consensus. Indeed, the way in which uncertainty has been treated
has evolved considerably since the first IPCC report, not least through the publication of
several guidance documents aimed at report authors [33]. By the time of the third report
(TAR: IPCC, 2001) some formal guidelines for the treatment of uncertainty were available
[34], while the authors of the fourth report (AR4: IPCC, 2007) had access to the more spe-Sustainability 2021, 13, 2466 7 of 12
cific Guidance Documents on Uncertainty Communication [35]. This was further devel-
oped in the Guidance Note for Lead Authors of the IPCC Fifth Assessment Report on
Consistent Treatment of Uncertainties[18], which established a clear set of criteria for ex-
pressing the degree of certainty associated with the findings and conclusions presented in
this report (AR5: IPCC, 2014). By contrast, the first two IPCC reports were much more
imprecise in their treatment of uncertainty—this was especially the case in the first report
(FAR; IPCC, 1990, 1992).
3.2. Evolution of Uncertainty
Our analysis considered a total of 837 statements distributed unevenly across the re-
ports (from 383 in IPCC2 to 87 in IPCC4), each of which was rated from 1 to 5 according
to the level of uncertainty expressed. As we will see, the trend over time is towards greater
uncertainty in the statements made.
As seen in Table 3, the largest number of uncertainty-related expressions, 383 (46%
of the total), are found in IPCC2, a lengthy text with only a few figures (in the summaries
produced by WGII and WGIII) and which makes frequent use of conditional statements.
The report with the second highest number of such expressions (23% of the total) is IPCC5
(AR5), and most of these statements are accompanied by the corresponding level of un-
certainty. Next comes IPCC3 (AR3), with 21% of the total number of uncertainty-related
expressions. Finally, the report with the smallest proportion of such expressions (10%) is
IPCC4 (AR4), which is also the shortest and a document containing numerous tables and
figures, which were not considered in our analysis.
Table 3. Level of uncertainty for the statements analyzed in each of the reports.
IPCC3 (TAR/AR3)
IPCC2 (SAR) (1995) IPCC4 2007 (AR4) IPCC5 2014 (AR5)
(2001)
Expressions of Confidence 383 172 87 195
Very High 11 (2.9%) 25 (14.5%) 25 (28.7%) 50 (25.6%)
High 115 (30%) 49 (28.5%) 35 (40.2%) 87 (44.6%)
Medium 179 (46.7%) 81 (47.1%) 20 (23.0%) 50 (25.6%)
Low 55 (14.4%) 13 (7.6%) 5 (5.7%) 3 (1.5%)
Very Low 23 (6%) 4 (2.3%) 2 (2.3%) 5 (2.6%)
In terms of the proportion of statements at each level of uncertainty the most notable
shift occurs between AR3 and AR4. Up until AR3, statements are most commonly ex-
pressed with a medium level of uncertainty, whereas from AR4 onwards the highest pro-
portion of statements corresponds to the higher certainty level; in addition, the percentage
of statements of very high certainty in AR4 and AR5 is at least equivalent to or even higher
than the proportion expressed with a medium level of uncertainty. One possible reason
for this increase in certainty is that climate science really took off around the turn of the
century, as is illustrated by the number of articles being published on the topic of climate
change [36]. A quick search of the publication databases shows that the number of articles
labeled “climate change” increased from 2500 in the year 2000 to 27,000 in 2019 (Scopus),
or from 20,000 to 78,000 over the same period according to Google Scholar (see Annex 2).
The other factor that may account for the shift in certainty level is that it coincides with
the introduction of clearer criteria for the treatment of uncertainty by the lead authors of
IPCC reports. [37].
If we analyze the uncertainty indicators according to the two broad categories we
defined earlier, namely “Call to action” (Very High + High confidence) and “No call to
action” (Medium + Low + Very Low confidence), we can gain an idea of the extent to
which the different reports may have served to encourage action on the part of policy-
makers (see Table 4). If the data from WGI or certain recommendations made by WGII or
WGIII with regard to adaptation or mitigation are presented with a very high or high level
of confidence (defined here as implying a “Call to action”), then policymakers may beSustainability 2021, 13, 2466 8 of 12
more motivated to take action than would be the case for statements made with very low,
low or medium levels of confidence (“No call to action”) [38–40].
Table 4. Grouping of statements for each report according to whether they implied a “Call to action” or “No call to action”.
IPCC3 2001
IPCC2 1995 (SAR) IPCC4 2007 (AR4) IPCC5 2014 (AR5)
(TAR/AR3)
Call to Action (%) 32.8 43 68.9 70.2
No Call to Action (%) 67.1 56.9 31 29.7
Mean Level of Certainty 3.09 3.45 3.87 3.89
It can be seen in Table 4that up until AR3 the level of confidence associated with the
content of reports remained oriented towards “No call to action” (56.9% of statements),
whereas a strong shift towards “Call to action” is observed in AR4 (68.9% of statements
expressed with high or very high confidence). In other words, while the majority of state-
ments in the summaries of SAR and AR3 did not conclusively constitute a “Call to action”
on the part of policymakers, this situation had clearly reversed by the time of AR4, and in
AR5 over 70% of statements are associated with a high or very high level of confidence.
Applying the criterion of mean level of uncertainty to the IPCC Summaries for Poli-
cymakers, it can be seen that the mean rating for the level of certainty increases progres-
sively from 3.09 in SAR to 3.89 in AR5 (Table 4). The problem with assigning a numerical
value to the level of certainty expressed in the reports is that the way in which they are
written favors the midpoint of 3 for qualifiers. The authors tend to include those state-
ments for which there is agreement or consensus, and also greater likelihood, and hence
the midpoint of 3 has greater weight. [41]. It should also be noted that this numerical rat-
ing of certainty varies much less significantly across the four reports (from 3.09 to 3.89)
than do the percentages reflecting the number of statements made with a high or very
high level of confidence, those implying a “Call to action” (from 32.8% to 70.2%).
4. Discussion
The dangers posed by climate change are not tangible nor visible in day-to-day life,
this poses a well-known paradox, the Giddens’s paradox [42] that leads decision makers
to wait until the dangers are so visible that are inevitable. Adding uncertainty to the sci-
entific assessments and projections about climate change adds tension to the communica-
tion of those outcomes [43]. Scientific uncertainty may be used to stimulate political and
social controversy, and to try to show to the public an untrue lack of scientific consensus
[44,45]. Many stakeholders track the process of decision making, from governments to the
general world population, including all kinds of international organizations and corpora-
tions, with many different points of view and perspectives [46,47] The IPCC reports and
the degree of certainty expressed in those assessments may be perceived very differently
depending on the observer’s educational background, and between observers from dif-
ferent countries. [48,49]
Science, facts and knowledge about climate change and how to respond to the chal-
lenges it poses to humanity, are a complex political, economic and also linguistic [50] and
communication issue that has evolved through pacts, protocols and treaties during the
last 30 years. [51–55]
In recent times, especially after the Paris agreement, and the “post truth politics” in sev-
eral countries, the communication of IPCC scientific assessments and mitigation solutions
communication has entered a new era more committed to specific and active action [56].
Knowing the high complexity of the decision making and the international political
agreements, we have drawn a timeline that will track the publication of IPCC reports in
relation to the main climate change agreements (see Table 5 and, especially, our analysis
of “Call to action”.Sustainability 2021, 13, 2466 9 of 12
The background to these initiatives is to be found in the 1980s, a decade that saw the
emergence of environmental movements and the start of increased interest in climate
change research [51], which we have already commented on. The increase in public and
scientific awareness about climate change was echoed in greater involvement on the part
of political authorities, both national and international, and led ultimately to the establish-
ment of the Intergovernmental Panel on Climate Change in 1988.
Table 5. Timeline showing the year of publication of IPCC reports and significant actions in the form of international
agreements.
IPCC Year Agreement Comments
IPCC Established 1988
IPCC1 1990/92 (FAR) 1990
1992 UNFCCC signed
IPCC2 1995 (SAR) 1995
1997 Kyoto signed 84 signatories
IPCC3 2001 (TAR/AR3) 2001
2005 Kyoto effective 55% of emissions
IPCC4 2007 (AR4) 2007
Hope that the Kyoto Protocol would be
2009 COP Copenhagen
renewed before expiry
2013 Kyoto expires Had been signed by 192 parties
IPCC5 2014 (AR5) 2014
2015 COP21 Paris Agreement 192 signatories
The first IPCC report (1990) drew together the literature predicting global warming
as a result of fossil fuel emissions and it reflected the predominant view among scientists
that urgent action was needed to avoid the damaging impact of climate change. This re-
sulted in the creation of the United Nations Framework Convention on Climate Change
(UNFCCC) and the signing of an international treaty in 1992. The UNFCCC established
the Conference of the Parties as its main decision-making body, under whose aegis the
Kyoto Protocol would later be signed in 1997 [52,53].
The second IPCC report, published in 1995, was much more cautious in its statements
of current scientific knowledge about global warming and climate change. When the
Kyoto Protocol was adopted in 1997, two years after publication of the SAR (in which
67.1% of statements classified as “No call to action” in our analysis), it only had 84 signa-
tories and did not garner the support of several major powers including the USA, China
and Canada. The lack of national and international bodies’ commitment caused great dis-
appointment to the chair of the IPCC [54].
Regarding the third IPCC report (2001), “Call to action” was still fairly weak (43% of
statements in our analysis), and it was not until 2005 that the key requirement of the Kyoto
Protocol was achieved, namely for binding targets by no less than 55 Parties who in total
accounted for at least 55% of global carbon dioxide emissions. It thus took eight years for
the Kyoto Protocol to come into force [55].
Our analysis of the fourth IPCC report (2007) indicated a much stronger “Call to ac-
tion” (68.9% of statements were high or very high confidence). By the time of the Confer-
ence of the Parties 15 (COP15) in Copenhagen in 2009, it was hoped that either a new
agreement would be reached, or the Kyoto Protocol would be renewed and extended be-
yond its scheduled expiry in 2012, although the latter did not ultimately come about. At
the time of expiry, the Kyoto Protocol had 192 signatories [56,57].
Finally, AR5, published in 2014, continued to make a stronger “Call to action”, with
70.2% of statements made to a high or very high level of confidence. One year later, the
Paris Agreement was adopted by 192 parties (out of a possible 197 signatories) in Decem-
ber 2015 [58–60].Sustainability 2021, 13, 2466 10 of 12
5. Conclusions
The level of certainty in the scientific assessments published in the different IPCC
reports since 1990 has increased as the published knowledge about climate and climate
change has become more robust and widespread.
Our content analysis of the degree of certainty associated with the scientific assess-
ments of these summaries for policy makers shows a progressive increase over the years,
and this is especially apparent when statements are grouped into two categories: those
expressed with a high or very high level of confidence versus those of medium, low or
very low confidence. The proportion of the former group has increased from 32.8% in
IPCC2 to 70.2% in IPCC5.
There are a great number of factors of all kinds that tackle with the politics of climate
change governance: but viewed from a historical perspective, in which the main climate
change agreements can be time lined to the publication of the various IPCC reports, the
relevant growing level of confidence in climate science, markedly in the last two reports,
and the corresponding need for policymakers to take action, may have contributed to the
more widespread adoption and ratification of these agreements. Indeed, our analysis sug-
gests that the level of certainty expressed in the reports is likely to have been a relevant
factor in the process of decision making that led to international protocols and accords
aimed at mitigating or reducing the impact of climate change.
In sum, the increasing scientific consensus that is reflected in higher levels of confi-
dence and the stronger likelihood of model predictions, and the communication of this
information to society, has encouraged stronger action and greater commitment on the
part of governments to the mechanisms of international cooperation designed to tackle
climate change.
Author Contributions: Conceptualization, T.M. and E.A.; methodology, T.M.; formal analysis,
T.M.; investigation, T.M..; data curation, T.M.; writing—original draft preparation, T.M.; writing—
review and editing, E.A.; supervision, E.A.; funding acquisition, E.A. All authors have read and
agreed to the published version of the manuscript.
Funding: This research was funded by AGAUR, research agency of Generalitat de Catalunya, Spain
(SGR 2017-422).
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Not applicable.
Conflicts of Interest: The authors declare no conflict of interest.
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